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Manage resources on overcommitted KVM hosts

Feb 13, 2011, 15:04 (0 Talkback[s])
(Other stories by Adam Litke)

"Summary: A key benefit of virtualization is the ability to consolidate multiple workloads onto a single computer system. This consolidation yields savings in power consumption, capital expense, and administration costs. The degree of savings depends on the ability to overcommit hardware resources such as memory, CPU cycles, I/O, and network bandwidth. Technologies such as memory ballooning and Kernel Same-page Merging (KSM) can improve memory overcommitment with proper manual tuning. Autonomic reconfiguration of these controls in response to host and VM conditions can result in even greater savings. In this article, learn how to apply these techniques to increase your savings.

"Virtualization promises to increase efficiency by enabling workload consolidation. Maximizing virtual machine density while maintaining good performance can be a real challenge:

* A workload's utilization of resources such as CPU, memory, and bandwidth for network and storage access varies over time; if you can dynamically allocate these resources according to demand, then you can achieve greater density with overcommitment.

* Optimal resource management also depends on factors such as the system configuration and hardware setup.

"One way to develop a management strategy that incorporates both factors is to write a set of rules in a policy language. You can tailor your policy to your unique conditions and effectively balance your consolidation and performance goals.

"This article explores the challenges associated with aggressive overcommitment and proposes a policy-driven management tool that can help you address the challenges. The tool is deployed in a typical KVM environment and manages two distinct workloads. This article evaluates the results of this exercise and concludes with suggestions for additional work items and potential research topics."

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